Nanny background check

We’re hiring a nanny and need to run a background check. There are a jillion out there, so we don’t need help finding one so much as advice choosing between them. Anyone have good/bad experience? Know of a reputable review site? Since it’s for a nanny (who, aside from hanging out with the Dudeling, will be left alone in a room with the equalizer sliders), we’d like to be as sure as possible.

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